Births outside of marriage have been on the decline according to a report from the CDC.

The number of unmarried births in 2013 totaled 1,605,643 which is the lowest it has been since 2005.

Fewer unmarried women under 35 are having babies. The CDC found reductions in births out of marriage for all age groups under 35. However, those over 35 have not shown a decline.

Births to unmarried women account for almost 60 percent of births.

This is still higher than previous generations of mothers, but a decline nonetheless.

"Since the 1940s, except for a few brief periods, there has been almost a continued increase in non-marital childbearing," said the author of the report Sally Curtin.

The number of unmarried births that occur are tracked because of possible complications such as premature delivery, low birth weight and infant death.

Most of the unmarried births are from couples in co-habiting unions. Only 15 percent of the births are from teenage-pregnancies. The unmarried mothers' birth rate among teenagers ages 15-17 had the largest decline with the rate dropping by almost a third between 2007 and 2012. Additionally, the rate for older unmarried teens fell by more than one-quarter.

"What's happened is the percent of nonmarital births within cohabitating unions has been increasing, but now it's increased to the point where the majority of nonmarital births are to women that are cohabitating," Curtin said.

The drop in births in unmarried women mirrors the overall decline of births in the United States.

Beginning with the recession, births have decreased, especially in the areas that were the worst hit by the economic crisis.

The birth rate decline was more prominent for Black and Hispanic women, and the birth rate among unmarried Hispanic women dropped by 28 percent between 2007 and 2012.

In unmarried women over the age of 35, however, there has been an increase in birth rate. According to the report, women in their late 30s had a 7 percent higher birth rate in 2012 than five years ago. The birth rate in women 40 to 55 increased by 29 percent from 7 in 1,000 births to 9 in 1,000 births.

Part of the reason for an increase in births from unmarried women is that couples are not rushing into marriage as much, choosing instead to become more financially secure. When the couples become pregnant, they are more likely to move in with one another.

Previous research has shown, also, that children in two-parent families tend to do better.